The present invention relates to a fluid pressure rodless cylinder of the kind having a cylinder with longitudinally extended slot, an external workpiece with a transfer member adapted to move along the slot and connected to a piston reciprocally movable within the cylinder.
Rodless pressure cylinders have existed in industry for many years. The advantage of such cylinders is that the cylinder length only insignificantly exceeds the stroke length. Rodless cylinders in general include a slotted cylindrical fluid pressure chamber and means for transferring the reciprocal movement of the piston to an external workpiece. In such cylinders this means normally includes a transfer bracket connected directly with the workpiece and piston, and a seal member along the length of the cylinder. Such a seal member is needed to prevent the fluid pressure from escaping the cylinder through the slot passed by the transfer bracket.
Of the prior attempts made to improve sealing, one device is shown in U.S. Pat. No. 3,820,446 and contemplates the use of a flat sealing member having magnetic properties. The sealing member is retained in sealing position by a number of magnetic elements embedded within the non-magnetic cylinder wall. A second device is shown in U.S. Pat. No. 4,373,427. This patent contemplates that the cylinder wall will be made of material having magnetic properties and the sealing member would have a portion constructed of a rubberized magnet. Both of these devices employ magnetic properties of the construction materials for sealing the longitudinal cylinder slot. A third sealing structure is shown in the U.S. Pat. No. 4,545,290. The device of this patent contemplates that the sealing member will be constructed of a flexible material and would include sealing portion for creating a seal against the inner side wall and support portion for insertion within the cylinder slot to retain the sealing member within the slot during an absence of pressure within the cylinder.
While all of the above mentioned devices provided satisfactory performance, there are ways to improve certain features of fluid pressure actuation capabilities at a reduced cost. Efforts are being made to construct a fluid pressure actuator of the rodless type without a sealing member. Further efforts are also being made to improve fluid power consumption and wearability by decreasing friction forces of the moving parts.